Paired-associate learning by normal children and retardates with relevant redundant compound stimuli

During daily sessions four first-grade boys each played a two-choice marble dropping game. When one colored light was presented a plain token was dispensed as soon as S dropped a marble, and when another light was on a token with a hole in its center was delivered. During choice trials that were interspersed among single-color trials S had to choose one of the two different colored holes. At the end of each session S traded tokens with holes for pennies and then turned in the remaining plain tokens which were not exchanged for money. After S had developed a preference for the response that earned the tokens with holes (tokens that were backed up with pennies) E instructed S to try to get as many plain tokens (unexchangeable tokens) as he could. All Ss immediately switched to the response that earned unexchangeable tokens but as soon as E left they returned to choosing the backed up response. When the adult reentered, Ss again chose to work for unexchangeable tokens. Two different Es (male and female) served and the instructions of each were effective in controlling responding as long as the adult was present, except for one S who did not respond to one E, but did respond as described for the other.     

Representational development of the human figure in familial retardates.

Representational development of the human figure of normal and familially retarded children was examined. Five tasks were employed: Drawing a Person, Figure Completion, two Form Puzzles, and Drawing on Dictation. Ss included 34 normal children, ages 3-0 to 5-10, and 34 familially retarded children, ages 4-4 to 13-1. The two groups were matched for mental age, socioeconomic status, public school attendance, and intact family structure. Results indicate that familial retardates performed as well as normals and at times surpassed them. Performance on these representational tasks is, predominantly, a function of mental age which lends support to a "developmental" theory of familial retardation and refutes the "defect" hypothesis.     

Feature positive discriminations in adults and children

The present experiment examined whether children and adult students differ in cognitive strategy used to solve a serial feature positive discrimination. The participants learned to make a specific response (R) to a target stimulus (T) when it was preceded by a feature stimulus (F) and to refrain from responding to T when presented alone. This discrimination can be solved in two distinctively different ways: by forming a direct relation between F and R (simple associational strategy), or by F indicating the T–R relation (higher-order relational strategy). The strategy used was examined by means of a transfer test and a counterconditioning manipulation. The results suggest that, for both the children and students, responding during the transfer test was under the control of the simple associational strategy. However, retest responding was controlled by a higher-order relational strategy more in the students than in the children. These results were discussed in the framework of previous findings in the developmental literature on age differences in type of cognitive strategy.     

Similarity between concurrent visual discriminations: Dimensions and objects

Accuracy is of ten reduced when two visual discriminations must be made concurrently (“divided attention”). According to a hypothesis originally proposed by Treisman (1969) and Aliport (1971), this result should depend on the similarity of required discriminations. When discriminations concern different visual dimensions, they should be made in somewhat separate visual subsystems, reducing interference between them. This prediction was tested in two experiments, involving discriminations of shape, size, orientation, and spatial frequency. In differentconditions of divided attention, concurrent discriminations concerned either the same or different dimensions, and either one or two objects. The results showed that performance depends only on the number of relevant objects, not on the number or similarity of required discriminations. They suggest that selective attention to an object is a coordinated state in which the outputs of multiple visual subsystems are made concurrently available for control of behavior.     

ERPs associated with visual duration discriminations in prefrontal and parietal cortex

An event-related potentials (ERP) study was undertaken to examine the role of prefrontal and parietal association cortices on selective attention and short-term memory functions in a duration discrimination task. Subjects performed better when discriminating the first stimulus relative to the second and not the reverse. Two contingent negative variations (CNV) were obtained for each stimulus duration at prefrontal regions, as well as two P300s at parietal regions. The CNV(S1) component recorded during the first stimulus (S1) appeared to be involved in selective attention at bilateral sites, while the P300(S1) component in the left hemisphere may be implicated in retaining it. The CNV(S2) wave, displayed during the second stimulus (S2), at bilateral sites and the right-sided P300(S2) wave seem to be implicated in working memory. The results indicate that recorded activity at prefrontal and parietal association cortices is tightly linked to task parameters and behavioral performances.     

Anchoring and relational judgments by young children and retardates

In five experiments using as dimensions brightness, texture, facial happiness, height, and weight, young children (ages 3.4 to 5.3 years) rendered bipolar judgments of stimuli intermediate in value between alternately given extreme anchors. Consistent relational shifts away from the anchors were found for all dimensions judged, and these effects proved virtually independent of children’s ages, the sequential orders of stimulus and anchor presentation, or the provision of overt visual memory props. Evidence of relational judgment within the narrower range of the test stimuli alone was also found. Essentially similar relational judgments were replicated with a sample of severe adult mental retardates.     

A computer touch-screen apparatus for training visual discriminations in rats.

We describe an operant conditioning apparatus that uses computerized touch-screen technology and is designed for the versatile and highly controlled testing of rats in a potentially wide variety of behavioral paradigms. Although computer-controlled touch-screen systems have been developed for use with pigeons, monkeys, and humans, analogous technologies and methods have not yet been developed for rats. The development of a touch-screen system for rats could enhance the efficiency of behavioral research with rats, and may offer a unique tool for studying animal learning. In the first test of the utility of the apparatus, 3 Sprague-Dawley rats learned to activate the touch screen only after the touch-screen panel was made slightly movable. These animals then learned to discriminate visual stimuli presented on the computer monitor, but only after the food magazine and pellet dispenser were moved to the rear of the chamber opposite the stimulus display and response window. In a test of the utility of the modified apparatus, 6 Long-Evans rats learned to activate the touch screen and learned one of three different simple discriminations using computer-generated, visually presented stimuli. A basic method for training rats to activate the computer touch screen and for visual discrimination training is described. Results show that rats learned to activate the touch screen and discriminate visual stimuli presented on a computer monitor. Potential applications and advantages of the touch-screen-equipped rat operant conditioning chamber are discussed.     

Analysis of a guided-response procedure in visual discriminations by rats.

A guided-response procedure was used to train a visual pattern discrimination by rats in a modified Sutherland box. The method consisted of guiding the animal to the correct choice by means of a retractable bridge that led to reinforcers, followed by gradually removing this prompt. This method was compared to a stimulus-fading procedure, in which the initial differences between discriminative stimuli were gradually faded until they differed only with respect to the critical dimension for discrimination, and to a trial-and-error procedure. Both gradual procedures resulted in fewer errors compared to the trial-and-error procedure. The higher efficiency of the fading procedures was attributed to less aversiveness derived from performance with few errors and to the use of step-by-step requirements relative to the criterion performance.